The present invention relates generally to a wheel hub with an integral brake and reducer, of the kind employed, for example, in industrial vehicles, agricultural machines, public works machines, or load-handling machines such as cranes or bridge-layers.
In general, such a wheel hub comprises a hollow body which, internally, is mounted to rotate on a fixed support sleeve, generally called a stub, and on the outside of which cab be attached, by its lateral extension, the wheel in question, and, in the said hollow body, in order to reduce its speed of rotation in use to a permissible value, a wheel reducer whose pinion-carrier is locked on the hollow body while the pinion shaft is intended to be locked on a wheel shaft mounted to rotate in the stub, and, in addition, for braking the whole unit when required, a brake comprising at least one brake disc which, being itself also intended to be locked in rotation to the said wheel shaft, either directly or indirectly, is capable of being subjected to an axial clamping force under the control of a suitable control unit, most frequently through the intermediary of a pressure plate.
When, as is most frequently the case, the hollow body is tubular overall, being closed transversely at the side opposite the stub by a removable cover which bears axially on it and which, in practice, is attached to it by screws engaged in the thickness of its section, the pinion-carrier is most frequently formed directly by such a cover, and is an integral part of the latter.
This is the case, for example, in the construction described in French Patent Application filed on Apr. 3, 1981 under No. 81/06,903 and published under No. 2,479,746.
This is also the case in the construction described in International Patent Application filed on May 28, 1980 under No. PCT/US80/00,644. and published under No. WO 81/03,469.
In French Patent Application filed on Nov. 23, 1981 under No. 81/21,885, however, the pinion-carrier consists of a part which is separate from the cover. In fact, this French Patent Application relates to an arrangement according to which the brake is arranged on the end of the wheel hub in question, that is to say beyond this wheel hub relative to the axle on the end of which the latter is itself to be fitted.
Consequently, to form a corresponding compartment for the brake, the hollow body of the hub is extended by a crown, and the latter is closed transversely by a removable cover at its opposite end, whilst the said hollow body is itself formed of two shells which are suitably coupled face-to-face, whilst the pinion-carrier forms an integral part of that shell which is axially the furthest from the stub. Thus, in such a design, the pinion-carrier is a direct part of the hollow body.
Most frequently, in the wheel hubs with an integral brake and reducer of the kind in question, the control of the brake incorporated in the wheel hub is two-fold; to form a service brake, there is first of all a hydraulic control which, to be brought into action, must be connected to a source of fluid under pressure; to form a brake for emergency or for parking, there is then a mechanical control which, in contrast to the preceding, is prevented from intervening when it is connected to a source of fluid under pressure, which is different in practice from the aforesaid source, and which, under the stress of an elastic control device, for example a stack of Belleville washers, is brought into action only if its connection to this source of pressure is interrupted.
This is the case, for example, in International Patent Application No. 80/00,644 and in French Patent Application No. 81/21,885, referred to earlier.
In practice, in both cases, the control unit controlling the brake is arranged on that side of the brake disc which is opposite the cover, so that when this brake disc is clamped axially, it is this cover which, directly or indirectly, provides an axial support for the latter.
One of the problems to be solved in the production of wheel hubs with an integral brake and reducer is to permit a simplified release of the brake fitted to the wheel hub, and preferably, in practice, a manual release for this brake when, the latter having served as an emergency brake, its intervention is due to some defect.
With the wheel hub described in International Patent Application No. 80/00,644, referred to above, such a release requires not only the complete opening of the hollow body of the hub, with the complication that this implies, but also the removal of the wheel in question, which prevents the vehicle in question from being itself able then possibly to continue its course at a low speed towards a workshop which is more specialized in dealing with the defect which has caused the locking of the emergency brake in question.
In fact, in this International Patent Application No. 80/00,644, the screws ensuring the fixing of the cover to the hollow body also ensure the fixing to the latter of the lateral extension of the wheel in question.
The repair must therefore be carried out on site.
This is also the case, in practice, for the locking of the brake of the wheel hub described in French Application No. 81/06,903, referred to above, although in the latter, and similarly in French Application No. 81/21,885, also mentioned above, the hollow body has, for fixing the lateral extension of the wheel, a special shoulder forming a flange which is separate from the cover, and which extends to a circumference of a diameter which is greater than that of the circumference to which the latter extends, with the result that the withdrawal of this cover can normally be carried out independently of any untimely removal of such a wheel.
However, in this French Patent Application No. 81/06,903, with the cover itself forming the pinion-carrier, any withdrawal of this cover is excessively complicated.
This is not exactly the case in French Patent Application No. 81/21,885, in which, being arranged at a distance from the pinion-carrier and forming a part which is separate from the latter, the cover merely closes the compartment, or brake compartment, in which the brake is fitted.
However, even partial withdrawal of the cover is still undesirable in such a case to avoid any contamination, possibly by dust or other dirt, of the interior of the brake compartment.
This is why, for unlocking the brake manually, there are provided, in this French Patent Application No. 81/21,885, special screws which are engaged by screwing in tapped openings in the cover and are capable, by screwing, of pressing back the pressure plate, ensuring the axial clamping of the brake disc or discs comprised in this brake.
Although such an arrangement is satisfactory, it has the disadvantage of requiring the use of special parts, namely the screws in question.
The general object of the present invention, is an arrangement of this kind which permits easy manual release of the brake, if necessary without any special part being provided for this purpose.